Manning J E, Schmid C W, Davidson N
Cell. 1975 Feb;4(2):141-55. doi: 10.1016/0092-8674(75)90121-x.
Cot analysis shows that the haploid Drosophila genome contains 12 percent rapidly reassociating, highly reiterated DNA, 12 percent middle repetitive DNA with an average reiteration frequency of 70, and 70 percent single-copy DNA. The distribution of the middle repetitive sequences in the genome has been studied by an examination in the electron microscope of the structures obtained when middle repetitive sequences present on large DNA strands reassociate and by the hydroxyapatite binding methods developed by Davidson et al. (1973). At least one third by weight of the middle repetitive sequences are interspersed in single-copy sequences. These interspersed middle repetitive sequences have a fairly uniform distribution of lengths from less than 0.5 to 13 kb, with a number average value of 5.6 kb. The average distance between middle repetitive sequences is greater than 13 kb. The data do not exclude the possibility that essentially all of the middle repetitive sequences have the interspersion pattern described above; however, it is possible that some of the middle repetitive sequences of Drosophila are clustered in stretches of length much greater than 13 kb. The interspersion pattern of the middle repetitive sequences in Drosophila is quite different from that which occurs in the sea urchin, in Xenopus, in rat, and probably many other higher eucaryotes.
Cot分析表明，果蝇单倍体基因组包含12%快速复性、高度重复的DNA，12%的中度重复DNA，其平均重复频率为70，以及70%的单拷贝DNA。通过电子显微镜检查大DNA链上存在的中度重复序列复性时形成的结构，以及采用戴维森等人（1973年）开发的羟基磷灰石结合方法，研究了中度重复序列在基因组中的分布。至少三分之一重量的中度重复序列散布于单拷贝序列中。这些散布的中度重复序列长度分布相当均匀，从小于0.5 kb到13 kb不等，数均长度为5.6 kb。中度重复序列之间的平均距离大于13 kb。这些数据并不排除基本上所有中度重复序列都具有上述散布模式的可能性；然而，果蝇的一些中度重复序列有可能聚集成长度远大于13 kb的片段。果蝇中度重复序列的散布模式与海胆、非洲爪蟾、大鼠以及可能许多其他高等真核生物中的散布模式截然不同。
